Halogen-based flame resistants are conventionally broadly used as flame resistants to make coating compositions flame-resistant (see, for example, Patent Literature 1). However, this method, since having the problem of dioxins and flons generated from halogenated flame-resistants, cannot be said to be preferable on the environmental protection. Inorganic flame resistants such as aluminum hydroxide are also used as flame resistants to make coating compositions flame-resistant. However, aluminum hydroxide has the problem of decreasing physical properties, including the water resistance, of coating materials and base materials to which the coating materials have been applied.
There is also a method of coating plastics with inorganic coating materials for flame resistance. However, the inorganic coating materials are less flexible and liable to crack, and thus coating therewith as thick films is difficult. Therefore, though the coating materials have flame resistance, in the case of composites with plastics, heat by flame contact is transferred to plastics, which resultantly carbonize or spread fire. In the case of coating materials containing an organic binder, the organic binder carbonizes in flame contact. Therefore, plastics which have been coated with these coating materials are difficult to use for applications requiring non-carbonization such as applications to railway rolling stock.
Glass fiber sheets on which an inorganic coating agent has been applied are conventionally known as railway rolling stock illumination covers. However, glass fiber sheets which have been coated with a common inorganic coating agent or which are impregnated with the inorganic coating agent, in the case where the binder contains an organic component, have the problem of low nonflammability; and those, in the case where the binder is an inorganic component, have drawbacks of low flexibility and easy cracking.
Patent Literature 2 discloses a light diffusion sheet including at least one sheet of a glass fiber woven cloth and a pair of resin layers interposing the glass fiber woven cloth, wherein the resin layers are constituted of a thermosetting resin or photocurable resin such as a vinyl ester. Patent Literature 3 discloses a glass fiber sheet having at least one sheet of a glass fiber woven cloth, resin-coated layers composed of a thermosetting resin formed by being impregnated and solidified in the glass fiber woven cloth, and a bead layer on at least one surface of the resin-coated layers. However, either of these light diffusion sheets exhibits insufficient nonflammability and low flexibility.